U.S. patent number 3,967,438 [Application Number 05/569,238] was granted by the patent office on 1976-07-06 for rotary mower spindle assembly.
This patent grant is currently assigned to International Harvester Company. Invention is credited to Michael D. Tombers.
United States Patent |
3,967,438 |
Tombers |
July 6, 1976 |
Rotary mower spindle assembly
Abstract
An improved mower blade spindle assembly for a rotary mower is
provided with an outer shaft having circumferential slots and an
inner shaft rotatable within the outer shaft and having a diametral
drive pin extending through the slots, and a braking member axially
movably mounted on the outer shaft for rotation therewith, the
braking member having a braking surface disposed for engagement
with an interior surface of a support sleeve in which the outer
shaft is mounted and a cammed surface disposed for engagement with
the pin such that upon cessation of the input drive, the pin acts
against the cammed surface to shift the brake member axially to
engage the braking surfaces.
Inventors: |
Tombers; Michael D.
(Merrillville, IN) |
Assignee: |
International Harvester Company
(Chicago, IL)
|
Family
ID: |
24274627 |
Appl.
No.: |
05/569,238 |
Filed: |
April 18, 1975 |
Current U.S.
Class: |
56/11.3; 56/17.5;
192/223.3 |
Current CPC
Class: |
A01D
34/6812 (20130101); A01D 75/20 (20130101); F16D
59/00 (20130101); A01D 2101/00 (20130101) |
Current International
Class: |
A01D
34/67 (20060101); A01D 34/68 (20060101); A01D
75/20 (20060101); A01D 75/00 (20060101); F16D
59/00 (20060101); A01D 035/26 () |
Field of
Search: |
;56/11.3,17.5
;192/8R,18R,147,15,16,64 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Eskovitz; J.N.
Attorney, Agent or Firm: Sullivan; Dennis K. Harman; Floyd
B.
Claims
What is claimed is:
1. In a rotary mower having a housing, a vertical spindle assembly
mounted on said housing, a power input member mounted at the upper
end of said spindle assembly and adapted to be rotatably driven
from an associated source of power, and a rotary impact cutting
blade mounted to the lower end of said spindle assembly for high
speed rotation, the improvement wherein said spindle assembly
comprises a support sleeve having a first braking surface, a hollow
outer shaft journalled in said sleeve and having a circumferential
slot, an inner shaft mounted for rotation within said outer shaft,
a radially extending drive pin fixed in said inner shaft in
registry with said circumferential slot and extending therethrough,
a brake member having a second braking surface mounted on the
outside of said outer shaft for rotation therewith, said braking
member being axially movable on said outer shaft to engage said
first and second braking surfaces, said braking member further
having a cammed surface disposed for engagement with said drive
pin, the configuration of said cammed surface relative to said pin
being such that upon said source of power being interrupted and
said cutting blade overrunning said input member, said drive pin
axially shifts said brake member on said outer shaft to a position
engaging said braking surfaces.
2. The invention in accordance with claim 1 and said support sleeve
comprising a cavity, the top side of said cavity comprising said
first braking surface, the top side of said brake member comprising
said second braking surface.
3. The invention in accordance with claim 2 and the lower surface
of said brake member comprising said cammed surface, said drive pin
supporting said brake member.
4. The invention in accordance with claim 3 and said outer shaft
having a second circumferential slot diametrally disposed from said
circumferential slot, said drive pin extending diametrally through
said inner shaft and said second slot, said cammed surface
comprising a pair of diametrally disposed cam elements.
5. The invention in accordance with claim 4 and said outer shaft
having an axial slot, said brake member having a pin extending
within said slot, said pin being out of contact with said inner
shaft.
6. The invention in accordance with claim 1 and a helical torsion
spring disposed within said outer shaft, one end of said spring
being connected to said outer shaft, the other end of said spring
being connected to said inner shaft, said spring being loaded in
torsion by relative rotation of said outer and inner shafts upon
drive being transmitted to said input member.
7. In a rotary mower having a housing, a spindle means mounted on
said housing, an input sheave mounted on said spindle means and
adapted to be belt driven from an associated drive source, and a
high speed rotary cutting blade of an inertia considerably larger
than said input sheave mounted to said spindle means, the
improvment wherein said spindle means comprises a nonrotatable
supporting sleeve having an internal cavity, the upper boundary of
said cavity comprising a first braking surface, an outer shaft
journalled in said sleeve and having a plurality of circumferential
slots, the lower end of said outer shaft being positively connected
to said cutting blade, an inner shaft mounted for limited rotation
within said outer shaft, said input sheave being mounted on said
inner shaft, radially extending pin means affixed in said inner
shaft and extending through said circumferential slots, a brake
member having an upper surface including a second braking surface
adapted to complementally engage said first braking surface axially
movably mounted on the outside of said outer shaft above said pin
means for rotation therewith, said brake member further comprising
a lower surface including a plurality of cam surfaces in register
with said circumferential slots, said cam surfaces being disposed
for engagement with said pin means such that, upon cessation of
drive to said input sheave and said blade overrunning said input
sheave due to its inertia of rotation, said pin means moves in said
slots against said cam surfaces to shift said braking surfaces into
engagement, said braking surfaces being noncontacting when power is
supplied to said input sheave.
8. The invention in accordance with claim 7 and torsion spring
means having a first end connected to said outer shaft and a second
end connected to said inner shaft for inducing reverse rotation
therebetween upon cessation of power to said input sheave.
9. The invention in accordance with claim 8 and said torsion spring
means comprising a helical torsion spring disposed within said
outer shaft beneath said inner shaft.
10. The invention in accordance with claim 7 and said pin means
comprising a diametral pin, said plurality of said circumferential
slots comprising a pair of diametrally disposed slots.
11. The invention in accordance with claim 7 and said support
sleeve comprising substantially identical upper and lower sections
to permit the manual interchange thereof relative to the outer
shaft to provide a replacement first braking surface.
12. The invention in accordance with claim 7 and seal means
disposed between said support sleeve and said outer shaft on both
sides of said internal cavity in said support sleeve.
Description
BACKGROUND OF THE INVENTION AND THE PRIOR ART
This invention relates to rotary mowers and more particularly, to a
rotary mower having improved spindle means including an automatic
braking mechanism for stopping the rotation of the blade when the
input power is cut off.
In mowers of the walk behind type, the cutting blade is generally
attached directly to the engine mounted thereon. Consequently, when
the engine is stopped, the blade stops. Mowers of the type used on
garden tractors and riding mowers, however, are generally belt
driven from the engine. The belt drive usually is provided with a
clutch idler pulley which tensions the drive belt to drive the
mower thus permitting the garden tractor or riding mower to be
driven without engaging the mower. When the drive is declutched,
however, the mower blade acts as a flywheel and may continue to
rotate silently for a period of time after the power is shut off,
leaving a potential source of injury for the person who may reach
within the mower housing after declutching the engine to clear a
blockage.
Various people have attacked this problem using audible warning
mechanisms, such as an overrunning clutch; however, such devices do
not stop the blade and probably extend the period of rotation.
Others have developed mechanical braking devices such as the
clutch-brake devices described in U.S. Pat. No. 3,837,450 to Malion
et al. and U.S. Pat. No. 2,985,992 to Dowdle. These devices require
external actuation and means for declutching the drive as well as
means for braking, rendering them less useful for tractor mounted
mowers.
Still others have developed automatic mower spindle brake
mechanisms. U.S. Pat. No. 3,722,642 to Zurek et al. and U.S. Pat.
No. 3,731,472 to Kamlukin describe similar mechanisms wherein the
input sheave is threaded on the output shaft. Drive through the
input sheave rotates it up the threads to a stop producing a
driving coupling with the output shaft. When the mower blade
overruns the input sheave due to their different inertias, reverse
relative rotation occurs between the input sheave and the output
shaft and the input sheave rotates downwardly on the output shaft
threads to engage complemental braking surfaces on the sheave and
spindle support sleeve. While these devices perform their intended
function, it is found that the threaded connection between the
input sheave and the output shaft tends to make the device more
expensive and create wear problems. The wear problems are believed
to be caused by the rocking action of the sheave on the shaft
threads due to the offset nature of the loading on the input
sheave. This rocking action also can cause some vibration and noise
in the spindle assembly. Moreover, since the input sheave must be
external of the support sleeve, sealing of the unit is difficult
and the up and down movement of the sheave on the output shaft
tends to pump the lubricant out of the mechanism creating further
wear problems.
Accordingly, it is a general object of the invention described
herein to produce a rotary mower having a relatively inexpensive
blade spindle assembly which may be automatically braked upon
cessation of the input drive thereto and which is less subject to
wear problems.
It is a more specific object of the invention to provide an
improved automatic braking means for a mower spindle assembly
wherein the driving force is transferred to the output shaft
independently of the braking member.
It is a further object of the invention to provide an improved
mower having an automatic braking spindle assembly which is more
readily adaptable to being sealed.
SUMMARY OF THE INVENTION
These and other objects of the invention are met in a rotary mower
of the type having a housing, a spindle assembly mounted on the
housing, an input sheave mounted on the spindle assembly, and a
high speed cutting blade mounted on the lower part of the spindle
assembly within the mower housing, wherein the spindle assembly
comprises a support sleeve having a first braking surface, an outer
shaft journalled in the sleeve having a circumferential slot, an
inner shaft rotatable to a limited extent within the outer shaft, a
radial drive pin mounted in the inner shaft and extending through
the circumferential slot in the output shaft, and a brake member
axially movably mounted on the outside of the outer shaft for
rotation therewith, the brake member having a second braking
surface and a cammed surface disposed for engagement with the drive
pins such that upon cessation of the drive to the input sheave and
the cutting blade producing a relative rotation between the inner
and outer shafts, the drive pin moves against the cammed surface to
shift the brake member axially to engage the braking surfaces.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects and advantages of the invention will become apparent
upon reading the following detailed description and upon reference
to the drawings, in which:
FIG. 1 is a sectional elevation of an improved rotary mower
incorporating the novel aspects of applicant's invention; and
FIG. 2 is a partial view of the rotating members internal of the
support sleeve taken along the line 2--2 of FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
Turning now to the drawings, there is shown a section of a rotary
mower generally designated 10 which may be a single or multiple
spindle mower of the type generally known in the art, such as the
two spindle mower used on the International Cadet 76 Lawn Tractor
made by the International Harvester Company. The mower 10 includes
a housing 11 including a horizontal deck portion 12 and vertical
side portions 14 which enclose the mower blade for safety.
A vertical spindle assembly generally designated 20 is mounted to
the housing deck 12 as by bolt 15. Mounted at the top of the
spindle assembly 20 is a pulley or sheave 21 which is adapted to be
driven by a belt 22 from an associated source of power such as a
tractor engine (not shown), as is customary in the art. Mounted at
the bottom of the spindle assembly 20 is a mounting plate 23 to
which may be bolted, for ease of replacement, a mower cutting blade
24 of considerably larger inertia than the input sheave 21 which
extends parallel to the deck 12 within the housing 11. The mower
blade 24 is provided with impact cutting edges at its outer ends
and generally is rotated at high speed, for example about 3000 rpm
to produce a tip speed of the cutting blade of about 18,000 feet
per minute, for good cutting efficiency in grass. It will be
appreciated that all of the foregoing description is generally in
accordance with the art.
Focusing in greater detail on the novel aspects of our invention,
the spindle assembly 20 comprises a support sleeve 30 which, for
simplicity of manufacture and to permit an end for end reversal
thereof, comprises two substantially identical top and bottom
castings 31 and 32, the only difference therebetween being that one
may have a lubrication fitting 34 provided thereon. The castings 31
and 32 are provided with mating flanges which fit together to form
a mounting flange for the spindle assembly 20 to the housing deck
12. The support sleeve 30 is provided with an internal cylindrical
cavity 35, the upper end of the cylindrical cavity being provided
with a first frustoconical braking surface 36. An outer output
shaft 40 comprising a hollow cylinder or pipe is journalled in the
housing 30 by upper and lower roller bearings 41 for high speed
rotation. The upper portion of the support sleeve 30 is provided
with a shoulder portion 42 which supports a thrust bearing 44
sandwiched in between a pair of thrust washers 45, a snap ring 46
retaining the thrust bearing assembly in position relative to the
outer shaft 40. The thrust washers 45 also provide an upper grease
seal means for the housing. The lower end of the shaft 40 is
provided with a snap ring 47 which retains a washer 48 against an
annular step in the lower portion of the support sleeve 30, a
grease seal 49 being interposed between the retaining washer 48 and
the lower bearing 41. Thus the two snap rings 46 and 47 retain the
output shaft against axial play in the support sleeve.
The outer shaft 40 extends downwardly from the support sleeve 30
whereat it is welded to the blade mounting plate 23, a portion of
the shaft extending through the mounting plate and blade 24 to be
flush therewith. A helical torsion spring 50 of a diameter slightly
smaller than the inner diameter of the shaft 40 is inserted at the
bottom thereof, the spring 50 having its last coil extended
outwardly to engage a notch in the end of the outer shaft 40 as at
51. A cover plate 52 retains the spring 50 in the notch of the
output shaft and provides a bottom support therefor. An inner input
shaft 60 is mounted for limited rotation within the outer shaft 40
and has a diametral slot at the bottom end which receives the upper
coil of the spring 50. The hub 62 of the input sheave 21 is mounted
against rotation to the top end of the inner shaft 60 as by key 64,
a pair of snap rings 61 retaining the hub against axial movement on
the shaft. The inner shaft 60 is provided at its medial portion
with a diametral drive pin 65 which may be press fit therein. The
pin 65 extends radially through a pair of circumferential slots 66
diametrally disposed in the outer shaft 40 in axial registry with
the pin 65.
A brake member 70 comprising a cylinder having an upper braking
surface 71 complemental to the braking surface 36 in the support
sleeve 30 is mounted about the outside of the outer shaft 40 for
rotation therewith by a pair of diametrally opposed radial pins 72
which are press fit in the brake member 70 and extend inwardly to
engage a pair of diametrally disposed axial slots 74 in the outer
shaft 40 but which do not engage the inner shaft 60. The braking
member is thus free to move axially on the outer shaft 40 while
being maintained in rotation therewith by the pins 72, the slots 74
being of sufficient length to permit the braking surfaces 36 and 71
to engage. The lower end of the brake member 70 is supported by the
ends of the diametral pin 65 and is provided with a cammed lower
surface including a pair of diametrally disposed ramps or cam
elements 75 which are disposed to engage the ends of the pin 65
extending through the slot 66 in the outer shaft 40. The cam
elements 75 are so located on the braking member 70 so that when
the pin 65 is at one end of the circumferential slot 66, the
braking member is in a downward position disengaging the braking
surfaces 36 and 71 from contact and when the pin 65 moves toward
the other end of the slot 66, which it preferably does not contact,
it will operate against the cam elements 75 and move the brake
member 70 axially upward to engage the braking surfaces 36 and 71.
Assuming the rotation of the input sheave 21 in a clockwise
direction, as viewed from the top, which would rotate the inner
shaft 60 in the direction of the arrow "A" on FIG. 2 the ramp of
the cam element 75 would move downwardly from left to right as
shown.
In the operation of the mower 10, the spindle assembly 20 always
rotates in one direction, for example the direction A indicated on
the drawings. When power is supplied to the input sheave 21, as by
tightening the belt 22, connecting it with an associated source of
power, the input sheave 21 and the inner shaft 60 begin to rotate
in the A direction or clockwise as viewed from the top. The drive
pin 65 moves with the inner shaft 60 in the slot 66 of the outer
shaft 40 until it contacts the clockwise or left (as viewed in FIG.
2) end of the slot 66, thereby providing a driving connection
between the inner shaft 60 and the outer shaft 40. The outer shaft
40 then rotates, also in the clockwise direction, rotating the
cutting blade 24. As may be seen in FIG. 2, the brake member 70 is
resting on the pin 65 and is in its lowest position thereby
disengaging the braking surfaces 36 and 71 from contact. At the
same time the coil spring 50 is tightened in torsion by the
relative rotation between the inner shaft 60 and the outer shaft
40.
Upon interruption or cessation of the driving force to the input
sheave 21, the sheave 21 and the inner shaft 60 will tend to slow
down due to friction, windage, and the friction of the loose belt
22 on the sheave. Since the cutting blade 24 has a relatively high
inertia compared to the input sheave and inner shaft, it will then
overrun the input sheave and drive the outer shaft 40 at a faster
speed than the inner shaft 60, thereby producing a reverse relative
rotation therebetween thus moving the pin 65 toward the
counterclockwise or right end of the slot 66. The movement of the
pin 65 in the slot 66 forces the pin 65 to act against the cam
element 75 on the brake member 70 thereby forcing the braking
member 70 upward against the support sleeve 30, engaging the
braking surfaces 36 and 71. Both shafts again rotate at the same
speed and the braking surfaces 36 and 71 are primarily maintained
in engagement until the unit stops by the large difference in
momentum of the mower blade relative to the input sheave 21.
The helical torsion spring 50 serves two functions, both primarily
intended for use in the event that the belt 22 breaks, is thrown
off of the sheave 21, or otherwise provides no friction on the
sheave when declutched. In this case, the spring, which has been
tightened in torsion by the relative rotation of the inner shaft 60
and the outer shaft 40 during start up of the mechanism, causes
reverse relative rotation when the drive to the input sheave 21 is
interrupted. This reverse relative rotation is sufficient to engage
the braking surfaces and start the braking process as described
above. Braking then is primarily caused by the differences in
angular momentum between the input sheave 21 and mower blade 24,
the blade 24 having a considerably higher inertia than the sheave.
When the spindle assembly reaches low speed, the difference in
momentum may not be sufficient to maintain the braking surfaces in
contact. The resistance of the coil spring, however, is sufficient
to keep the pin toward the right side of the slot 66 and keep the
braking surfaces engaged.
It is noted that the braking member is not selfenergizing and the
amount of braking applied depends primarily on the difference in
momentum between the upper and lower pulley. Thus, the amount of
time required to stop the unit can be varied by varying the
inertial mass input sheave 21. Of course, it could also be changed
by varying the angle or area of the braking surfaces. Moreover,
because the brake is not self-energizing the braking torque does
not cause undesirable peak loads on the outer shaft 40 which could
cause a torsional failure of the shaft.
It is further noted that because the brake member is not
self-energizing, it will not have as great a tendency to stick in
the brake engaged position. Also, because the brake acts upwardly
rather than downwardly, the force of gravity on the brake member
also helps to free up the brake surfaces after braking although the
coil spring may maintain them in contact until driving is
resumed.
Thus it is apparent that there has been provided in accordance with
the invention a rotary mower spindle which fully meets the objects
and advantages set forth above. Those of ordinary skill in the art
will readily recognize modifications of the embodiment described
which may be made in view of the foregoing specification.
Accordingly it is intended to embrace all such modifications as may
fall within the scope of the appended claims.
* * * * *